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The outside diameter of a gear is the diameter of the addendum (tip) circle. In a bevel gear it is the diameter of the crown circle. In a throated worm gear it is the maximum diameter of the blank. The term applies to external gears, this is can also be known from major diameter. [1]
Meshing of two spur gears with involute external teeth. z 1 = 20, z 2 = 50, α = 20°, ξ 1 = ξ 2 = 0, ISO 53:1998. The lower (green) gear is the driving one. The line of contact, which is the locus of all teeth contact points, is shown in blue.
Module is a direct dimension ("millimeters per tooth"), unlike diametral pitch, which is an inverse dimension ("teeth per inch"). Thus, if the pitch diameter of a gear is 40 mm and the number of teeth 20, the module is 2, which means that there are 2 mm of pitch diameter for each tooth. [56]
The cylindrical gear tooth profile corresponds to an involute (i.e. a triangle wave projected on the circumference of a circle), whereas the bevel gear tooth profile is an octoid [definition needed] (i.e. a triangle wave projected on the normal path of a circle of a sphere).
A gear train or gear set is a machine element of a mechanical system formed by mounting two or more gears on a frame such that the teeth of the gears engage. Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping, providing a smooth transmission of rotation from one gear to the next. [ 2 ]
That combination of gears and wheel is said to be "26 gear inches." If the front chainring has 48 teeth and the rear sprocket has 24 teeth, then each turn of the pedals produces two turns of the rear wheel. This is equivalent to doubling the size of the drive wheel; that is, it is like a directly driven bicycle with a 52-inch wheel.
When two toothed gears mesh, an imaginary circle, the pitch circle, can be drawn around the centre of either gear through the point where their teeth make contact. The curves of the teeth outside the pitch circle are known as the addenda, and the curves of the tooth spaces inside the pitch circle are known as the dedenda. An addendum of one ...
In the case of Module (MOD) 4.0 spur gears: Normal spur gears (over 17 teeth) have a pitch circle diameter (PCD) equal to MOD × number of teeth. [4] Corrected spur gears (under 17 teeth) have a PCD equal to MOD × number of teeth + MOD. There are two types of corrected gears: S0 gearing (x1 + x2 = zero) S gearing (x1 + x2 ≠ zero)